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x86/mm/ptdump: Fix soft lockup in page table walker

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CONFIG_KASAN=y needs a lot of virtual memory mapped for its shadow.
In that case ptdump_walk_pgd_level_core() takes a lot of time to
walk across all page tables and doing this without
a rescheduling causes soft lockups:

 NMI watchdog: BUG: soft lockup - CPU#3 stuck for 23s! [swapper/0:1]
 ...
 Call Trace:
  ptdump_walk_pgd_level_core+0x40c/0x550
  ptdump_walk_pgd_level_checkwx+0x17/0x20
  mark_rodata_ro+0x13b/0x150
  kernel_init+0x2f/0x120
  ret_from_fork+0x2c/0x40

I guess that this issue might arise even without KASAN on huge machines
with several terabytes of RAM.

Stick cond_resched() in pgd loop to fix this.

Reported-by: Tobias Regnery <tobias.regnery@gmail.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Alexander Potapenko <glider@google.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170210095405.31802-1-aryabinin@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andrey Ryabinin 2017-02-10 12:54:05 +03:00 committed by Thomas Gleixner
parent 5f2e71e714
commit 146fbb7669
1 changed files with 2 additions and 0 deletions
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2
arch/x86/mm/dump_pagetables.c
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@ -15,6 +15,7 @@
#include <linux/debugfs.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <asm/pgtable.h>
@ -406,6 +407,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
} else
note_page(m, &st, __pgprot(0), 1);
cond_resched();
start++;
}